I've seen my first HMRC scam email today. NOT from HMRC although it appears to be (reading closely, it was from a Yahoo account). It had a zip file form attached to be completed to claim the refund.
These things are designed either deliver a virus or get you to fill in and send your bank details. Needless to say I didn't open the attachment.
The body of the email reads like this:

The contents of this email and any attachments are confidential and as applicable, copyright in these is reserved to HM Revenue & Customs.
Unless expressly authorised by us, any further dissemination or distribution of this email or its attachments is prohibited.

If you are not the intended recipient of this email, please reply to inform us that you have received this email in error and then delete it without retaining any copy.

I am sending this email to announce: After the last annual calculation of your fiscal activity we have determined that you are eligible to receive a tax refund of 244.79 GBP

You have attached the tax return form with the TAX REFUND NUMBER ID: 381716209, complete the tax return form attached to this message.

After completing the form, please submit the form by clicking the SUBMIT button on form and allow us 5-9 business days in order to process it.

Our head office address can be found on our web site at HM Revenue & Customs: www.hmrc.gov.uk